The invention relates generally to marine propulsion systems, and, more particularly to marine propulsion systems having reversing transmissions and to remote operation of such reversing transmissions by a link, such as a push-pull cable.
Remote actuation of a marine propulsion reversing transmission commonly involves operation of a remote single lever control to displace the inner core of the push-pull cable through a distance which is often in excess of the distance actually required at the marine propulsion system for shifting operation. The over-stroking that results may place unnecessary heavy loading and undesirable stresses on the push-pull cable and/or other shift linkage components.
In the past, attempts have been made to overcome the overstroke issue by interposing a spring in the operating linkage. However, use of such spring suffers from the following drawbacks: delay in shift timing, insufficient load to guarantee shifting, excessive loading after shifting, or over-shooting neutral if a neutral detent is not strong enough. Other designs produce the transmission shift stroke using a rotating shift rod with a horizontally mounted cam or a vertically offset crank pin at the lower end of the shift rod. In such designs overstroke is attempted to be corrected by providing a dwell section on one of the cam surfaces so that additional rotation of the shift rod does not result in additional stress in the shifting system. For example, the dwell section would avoid untimely engagement of a clutch, e.g., a clutch dog, in the transmission. Unfortunately, such designs require tight dimensional control for virtually every shift component. For example, in the foregoing cam design, close dimensional controls are required to ensure that the dwell section of the stroke occurs precisely at the point of full clutch dog engagement. Also, regardless of the close tolerances held on the shift linkage components, the remote control cable may have considerable dead or lost motion, which can vary greatly depending on cable length and the number of bends required in a given installation. To accommodate such lost motion in the cable, a marine engine manufacturer must design the various components of the shift linkage to operate under worst conditions, unfortunately, under most other operational conditions the cable will provide more stroke than necessary. In either case, when an overstroke condition develops, the shift rod, which is generally long and slender, twists as a torsional spring in rotary systems, or bows outward along its length in linear system, and the shift cable may buckle up or stretch inside its casing. It will be appreciated the virtually every shifting system component is subjected to greater stress during the overstroke condition.
In view of the above-described drawbacks, it is a desirable to provide a shift control assembly and techniques that allow for tolerating stroke that may be longer that is needed to shift the clutch in a transmission gearcase without stretching or compressing the push-pull cable and without inducing undesirable stresses in any other shift linkage components. It is further desirable that such assembly and techniques have the ability to return the clutch dog to neutral without having to first recover any initial over-stroke or over-travel. It is also desirable to provide a shift control kit that can be reliably and inexpensively installed either by the engine manufacturer or by authorized service providers as a retrofit kit in respective fleets of boats.
Generally speaking, the present invention fulfills the foregoing needs by providing a shift control assembly for a marine drive having a transmission with a clutch member movable between a neutral position and a respective drive position. The assembly comprises a first lever responsive to a remotely actuated link and a second lever is connected to drive the clutch member. The assembly further comprises a clutch subassembly interconnected between the first and second levers. The clutch subassembly is configured to selectively pivot the second lever to effect movement of the clutch member, and to permit over-travel of the link connected to the first lever without pivoting the second lever upon engagement of the clutch member in the drive position.
The present invention further fulfills the foregoing needs by providing clutch means for selectively pivoting the second lever to effect movement of the clutch member out of its respective drive position upon initial rotation of the first lever back toward neutral. The clutch means is configured to cause the second lever to pivot together with the first lever until the second lever has fully returned to neutral, at which point the first lever continues to pivot to its neutral position without causing further rotation of the second lever. At any point within the full range of rotation of the first lever, reversing the direction of rotation of the first lever will again immediately cause the second lever to pivot together with the first lever. Therefore, in operation, it is not necessary for the first lever to completely return to neutral should the operator decide to return to the fully engaged drive position. It will be appreciated, however, that both levers should preferably return to neutral before the operator can select the opposite drive position.
In another aspect of the invention, the foregoing needs are fulfilled by providing a method for providing shift control for a marine drive having a transmission with a clutch member movable between a neutral position and a drive position. The method allows for providing a first lever responsive to a remotely actuated link and for connecting a second lever to drive the clutch member. The method further allows for selectively pivoting the second lever to effect movement of the clutch member at least until engagement of the clutch member in the drive position and upon said engagement allowing over-travel of the link connected to the first lever without further pivoting of the second lever.